The secret to stopping a backstabbing peer is to show that the attacker, far from being constructive, is being unfair and personal. If the actions have been covert, deliver your message indirectly—that way the attacker can't simply deny involvement and end the conversation. If the attack was overt, or if the indirect approach doesn't work, deal directly. Ideally, you should conduct the discussion privately, which increases the chance of an honest exchange. But if that doesn't work, or if the attack is so damaging you must respond immediately, do it publicly. If all else fails, stress your willingness to take the dispute to a higher authority.
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